The role of coordination chemistry in biological systems, ranging from the traditional coordination chemistry of cations, to the host-guest chemistry of anions and neutral molecules, can not be understated. Important examples of coordination and host-guest chemistry in biological systems can be observed in the catalytic properties associated with metal ions in metalloenzymes, the base-pairing of nucleic acids, and the interaction of enzymes with substrates. In view of the complexity of biological systems, studies on smaller synthetic model systems may be used to provide key information in order to elucidate many fundamental biological processes. The thrust of this proposal is to develop some new model systems that will generate important information regarding the roles of both cationic and anionic species in biological systems. Specific goals include (i) introduction of a modified ligand systems for establishing well-defined structural and chemical models for carbonic anhydrase, an important enzyme with respect to aspects of respiration and intracellular CO2/HCO3- equilibration, and (ii) the synthesis and applications of series of new low-coordinate tripodal receptor systems that are designed to bind strongly, but to only one face of an anionic substrate. The aims of this research will be achieved by a combination of solution and solid-state studies. Single crystal X-ray diffraction will be used to determine coordination environments of the metalloenzyme models and also the detailed nature of the host-guest interaction in the solid state. 1H, 13C and 17O NMR spectroscopy will provide further characterization of the metalloenzyme models and also a means for measuring kinetic and thermodynamic parameters. A variety of spectroscopic techniques (e.g. 35C1 NMR spectroscopy) will be used to determine association constants and the strength of the host-guest interaction. Standard chemical techniques will be utilized to investigate applications of these receptor systems in areas such as chiral resolution and phase transfer catalysis.